In the traditional methods of hydroponic cultivation, of such plants as lettuce, an enviromentally-controlled growth chamber is provided. In this chamber, the plants are grown under strictly controlled conditions of light, temperature, and humidity. The nutrient and water supply to the plants is also adjusted and controlled with strict accuracy, as is the oxygen supply to the roots. The carbon dioxide content of the air above and around the plants is also carefully monitored, and adjusted as required.
The main benefits of hydroponic cultivation lie in the excellent and consistent quality of the product, and in the fact that the product can be supplied fresh every day, all the year round. Thus, the supermarkets and the hydroponic cultivators may cooperate to supply fresh lettuces, etc, to the consumer with great administrative efficiency, and at a minimum cost.
The disadvantage of hydronic cultivation has been that the production costs are rather higher than for lettuces etc grown in fields. Although hydroponic lettuces require far less water than lettuce grown in fields (which can be the overriding factor in arid regions) hydroponic cultivation requires more capital equipment, and requires the input of energy, in the form of electricity for the lights, and for the temperature and humidity control equipment. The labour costs of planting out and harvesting, however, are generally less in hydroponic cultivation.
In the growth chamber, the plants are grown in trays or troughs, under water. Oxygen is supplied to the roots, which have been usually bedded in gravel. Bright fluorescent lights are positioned above the trays. In hydroponic cultivation, the lights can be arranged to operate with an optimised spectrum cycle at all times; whereas the spectrum of natural sunlight is optimum only for a few hours per day.
It is an aim of the invention to provide a means by which hydroponic cultivation of food plants such as lettuce may be carried out more economically and profitably than has been the case hitherto.
It is an aim of the invention to provide, in the hydroponic cultivation of food plants, a means whereby economic utilisation of space, of energy, water, and nutrients, and of labour, may be achieved.